System and method for regulating EGR cooling using a rankine cycle

ABSTRACT

This disclosure relates to a waste heat recovery (WHR) system and method for regulating exhaust gas recirculation (EGR) cooling, and more particularly, to a Rankine cycle WHR system and method, including a recuperator bypass arrangement to regulate EGR exhaust gas cooling for engine efficiency improvement and thermal management. This disclosure describes other unique bypass arrangements for increased flexibility in the ability to regulate EGR exhaust gas cooling.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalPatent Application No. 61/426,972, filed on Dec. 23, 2010, which ishereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under “Exhaust EnergyRecovery,” contract number DE-FC26-05NT42419 awarded by the Departmentof Energy (DOE). The government has certain rights in the invention.

TECHNICAL FIELD

This disclosure relates to a waste heat recovery (WHR) system and methodfor regulating exhaust gas recirculation (EGR) cooling, and moreparticularly, to a Rankine cycle WHR system and method, including a heatexchanger bypass arrangement to regulate EGR cooling for engineefficiency improvement and thermal management.

BACKGROUND

Increasing the efficiency of internal combustion engines is critical tomeet customer expectations and an array of government-mandatedregulations. Internal combustion engines generate significant amounts ofheat that heat exchangers eventually transfer to the air surrounding theinternal combustion engine. If a portion of the wasted heat wererecovered by performing a necessary engine function, the efficiency ofthe internal combustion engine would be improved. However, the recoveryof this wasted heat can lead to conflict between the needs of twodifferent portions of an internal combustion engine. The resolution ofthis conflict can lead to improved engine performance and efficiency.

SUMMARY

This disclosure provides a waste heat recovery system for an internalcombustion engine. The waste heat recovery system comprises a fluidmanagement circuit and a waste heat recovery circuit. The fluidmanagement circuit includes a sub-cooler containing a liquid workingfluid and a pump fluidly connected to the sub-cooler. The pump isoperable to draw the liquid working fluid from the sub-cooler. Theliquid working fluid has a first temperature. The waste heat recoverycircuit includes a recuperator receiving the liquid working fluid fromthe pump and receiving a vaporized working fluid, wherein a transfer ofheat from the vaporized working fluid to the liquid working fluidincreases the temperature of the liquid working fluid. The waste heatrecovery circuit also includes an EGR boiler flow control valve fluidlyconnected in parallel to the recuperator and receiving the liquidworking fluid from the pump. The waste heat recovery circuit alsoincludes a boiler receiving an EGR exhaust gas at a first inlet, theliquid working fluid at the first temperature from the EGR boiler flowcontrol valve at a second inlet, and the liquid working fluid flowingfrom the recuperator at a third inlet. The liquid working fluid at thethird inlet is at a second temperature. Heat is transferred from the EGRexhaust gas to the liquid working fluid to cause the liquid workingfluid to vaporize. The liquid working fluid at the first temperature isused to control the amount of cooling provided to the EGR exhaust gas.

This disclosure also provides a waste heat recovery system for aninternal combustion engine. The waste heat recovery system comprises asub-cooler containing a liquid working fluid and a pump fluidlyconnected to the sub-cooler and operable to draw the liquid workingfluid from the sub-cooler. The liquid working fluid has a firsttemperature. The waste heat recovery system also comprises a recuperatorreceiving the liquid working fluid from the pump and receiving vaporizedworking fluid from an EGR boiler, wherein the temperature of the liquidworking fluid is increased by a transfer of heat from the vaporizedworking fluid to the liquid working fluid. The waste heat recoverysystem also comprises a heat exchanger fluidly connected to therecuperator, a first EGR boiler flow control valve fluidly connected tothe pump in parallel to the recuperator and a second EGR boiler flowcontrol valve fluidly connected to the recuperator and to the EGRboiler. The EGR boiler receives an EGR exhaust gas at a first inlet, theliquid working fluid at the first temperature flowing through the firstEGR boiler flow control valve at a second inlet, the liquid workingfluid flowing through the recuperator and the second boiler flow controlvalve at a third inlet, the liquid working fluid flowing through therecuperator and the heat exchanger at a fourth inlet. The liquid workingfluid at the third inlet is at a second temperature higher than thefirst temperature and the liquid working fluid at the fourth inlet is ata third temperature higher than the second temperature. Heat istransferred from the EGR exhaust gas to the liquid working fluid tocause the liquid working fluid to vaporize. The liquid working fluid atthe first temperature and the liquid working fluid at the secondtemperature are used to control the amount of cooling provided to theEGR exhaust gas.

This disclosure also provides a method for regulating EGR exhaust gastemperature in an engine using a Rankine cycle. The method comprisesdirecting a first portion of a liquid working fluid pumped from ssub-cooler through at least one heat exchanger and then to an EGRboiler. The method also comprises directing a second portion of a liquidworking fluid pumped from a sub-cooler through a bypass around the atleast one heat exchanger to the EGR boiler. The EGR boiler receives theEGR exhaust gas.

Advantages and features of the embodiments of this disclosure willbecome more apparent from the following detailed description ofexemplary embodiments when viewed in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a first exemplary embodiment of the presentdisclosure.

FIG. 2 is a schematic of a second exemplary embodiment of the presentdisclosure.

FIG. 3 is a schematic of a third exemplary embodiment of the presentdisclosure.

FIG. 4 is a schematic of a fourth exemplary embodiment of the presentdisclosure

FIG. 5A is a schematic of a first exemplary embodiment heat exchanger ofthe present disclosure.

FIG. 5B is a schematic of a second exemplary embodiment heat exchangerof the present disclosure.

FIG. 5C is a schematic of a third exemplary embodiment heat exchanger ofthe present disclosure.

FIG. 5D is a schematic of a fourth exemplary embodiment heat exchangerof the present disclosure.

DETAILED DESCRIPTION

Referring now to FIG. 1, an engine system 10 in accordance with a firstexemplary embodiment of the present disclosure is shown. Engine system10 includes a fluid management circuit 12, a portion of an exhaustcircuit 11, and elements that are part of a waste heat recovery systemor circuit 14.

Fluid management circuit 12 includes a sub-cooler 16, a condenser 18, areceiver 20, and a level control valve 22. Condenser 18 may be integralwith sub-cooler 16 or may be commonly mounted on a common base 24, whichmay include a plurality of fluid flow paths (not shown) to fluidlyconnect condenser 18 to sub-cooler 16. Receiver 20 may be physicallyelevated higher than sub-cooler 16 and is connected to sub-cooler 16through level control valve 22, which connects to receiver 20 by areceiver conduit 26 and to sub-cooler 16 by a sub-cooler conduit 28.Sub-cooler conduit 28 may connect directly to sub-cooler 16 or mayconnect indirectly to sub-cooler 16 by way of common base 24. Sub-cooler16 connects to a feed pump 32 by way of a pump conduit 30. Feed pump 32connects to a feed pump flow valve 34 by way of a feed valve conduit 36.Feed pump flow valve 34 connects to receiver 20 by way of a dump conduit38 and connects to a filter drier 42 by way of a filter drier conduit40.

Filter drier 42 connects to a recuperator 44 of waste heat recoverycircuit 14 by way of a recuperator conduit 46 and connects to an EGRboiler flow control valve 48 by way of a first boiler control valveconduit 50. EGR boiler control valve 48 connects to an inlet 74 c of anEGR boiler/superheater 74 by way of a second boiler control valveconduit 51. Recuperator 44 connects to a pre-charge air cooler (pre-CAC)52 by way of a pre-CAC conduit 54. Pre-CAC 52 connects to an exhaustheat exchanger 56 by way of an exhaust conduit 58. Exhaust heatexchanger 56 is also part of exhaust circuit 11.

Exhaust circuit 11 may include an aftertreatment system 60 that connectsto an exhaust gas control valve 62 by way of an aftertreatment conduit64. Exhaust gas control valve 62 connects to exhaust heat exchanger 56by way of a first exhaust gas conduit 66. Exhaust gas control valve 62also connects to a tailpipe or exhaust pipe 72 by way of a secondexhaust gas conduit 68. Exhaust heat exchanger 56 also connects totailpipe or exhaust pipe 72 by way of a third exhaust conduit 70.Exhaust gas heat exchanger 56 connects to an inlet 74 d of EGRboiler/superheater 74 of waste heat recovery circuit 14 by way of an EGRconduit 76. EGR boiler/superheater 74 is also an EGR cooler. EGRboiler/superheater 74 has an EGR inlet 74 a and an EGR outlet 74 b.

EGR boiler/superheater 74 connects to an energy conversion device 78 byway of a first conversion device conduit 80, which is connected to anoutlet 74 e of EGR boiler/superheater 74. Energy conversion device 78 ofRankine cycle WHR system 10 is capable of producing additional work ortransferring energy to another device or system. For example, energyconversion device 78 can be a turbine that rotates as a result ofexpanding working fluid vapor to provide additional work, which can befed into the engine's driveline to supplement the engine's power eithermechanically or electrically (e.g., by turning a generator), or it canbe used to power electrical devices, parasitic or a storage battery (notshown). Alternatively, the energy conversion device can be used totransfer energy from one system to another system (e.g., to transferheat energy from WHR system 10 to a fluid for a heating system).

Energy conversion device 78 may drive an auxiliary unit 82. Auxiliaryunit 82 may be part of a generator. If auxiliary unit 82 is a generator,it may feed a motor generator that may be part of a hybrid drive system.Energy conversion device 78 connects to recuperator 44 by way of asecond conversion device conduit 84. Recuperator 44 connects tocondenser 18 of fluid management circuit 12 by a condenser conduit 88.Recuperator 44 connects to receiver 20 by way of condenser conduit 88and a receiver vent conduit 86.

Engine system 10 includes a control module or control system 150.Control module 150, which may be a single processor, a distributedprocessor, an electronic equivalent of a processor, or any combinationof the aforementioned elements, as well as software, electronic storage,fixed lookup tables and the like, is connected to certain components offluid management circuit 12 and waste heat recovery circuit 14 by a wireharness 35, though such connection may be by other means, including awireless system.

Control module 150 connects to a fluid level sensor 13 associated withsub-cooler 16. Control module 150 connects to feed pump flow valve 34,EGR boiler flow control valve 48, and exhaust gas control valve 62.Control module 150 may connect to feed pump 32. Control module 150 mayalso connect to temperature sensors positioned within EGRboiler/superheater 74. Referring to FIG. 5A, control module 150 mayconnect to a first EGR temperature sensor 15, a second EGR temperaturesensor 17, a first working fluid temperature sensor 19, a second workingfluid temperature sensor 21, and a third working fluid temperaturesensor 23. Temperature sensor 17 and temperature sensor 19 may belocated in a lower temperature portion 25 of EGR boiler/superheater 74.Temperature sensor 15, temperature sensor 21 and temperature sensor 23may be located in a higher temperature portion 27 of EGRboiler/superheater 74.

Sub-cooler 16 stores liquid working fluid. If the level of liquidworking fluid in sub-cooler 16 is less than a predetermined level asdetermined by a working fluid level sensor 13, level control valve 22opens. Liquid working fluid from receiver 20 will then flow throughreceiver conduit 26, level control valve 22, and then sub-cooler conduit28 to enter either sub-cooler 16 or base plate 24 and then sub-cooler16, which are fluidly downstream of receiver 20.

An engine system 10 belt (not shown) or an electric motor (not shown)drives feed pump 32. Feed pump 32 pulls or draws liquid working fluidfrom sub-cooler 16 through pump conduit 30. Feed pump 32 then forcesliquid working fluid through feed valve conduit 36 to feed pump flowvalve 34. Feed pump flow valve 34 has two functions. Control module orcontrol system 150 of engine system 10 monitors the cooling function ofwaste heat recovery circuit 14. If waste heat recovery circuit 14requires additional liquid working fluid, control module or controlsystem 150 of engine system 10 directs proportional feed pump flow valve34 of fluid management system 12 to provide additional liquid workingfluid to waste heat recovery circuit 14 through filter drier conduit 40.Proportional feed pump flow valve 34 directs any liquid working fluidnot required by waste heat recovery circuit 14 to receiver 20 by way ofdump conduit 38.

Filter drier conduit 40 connects liquid working fluid to filter drier42. The function of filter drier 42 is to trap moisture, particulatesand other contaminants that might interfere with or cause damage to theoperation of waste heat recovery circuit 14. In an existing Rankinecycle configuration, the liquid working fluid flows downstream fromfilter drier 42 through recuperator conduit 46 to recuperator 44. Heattransfers from the hot vaporized working fluid returning to condenser 18from energy conversion device 78 by way of second conversion deviceconduit 84 and recuperator 44 to the cooler liquid working fluidentering recuperator 44 by way of recuperator conduit 46. As will beseen, the cooler liquid working fluid coming into recuperator 44 by wayof recuperator conduit 46 may need to be heated to a level sufficient toperform useful work in EGR boiler/superheater 74, and recuperator 44 mayprovide a first step in the heating process. While helping to heat theliquid working fluid coming into recuperator 44 by way of recuperatorconduit 46, vaporized working fluid entering recuperator 44 by way ofsecond conversion device conduit 84 is cooled prior to enteringcondenser 18.

From recuperator 44, liquid working fluid now travels downstream topre-CAC 52 by way of pre-CAC conduit 54. Pre-CAC 52 receives air from anengine system 10 turbocharger compressor 53. The air from turbochargercompressor 53 is heated by action of turbocharger compressor 53. Pre-CAC52 transfers some of the heat from that compressed air to the liquidworking fluid entering pre-CAC 52 by way of pre-CAC conduit 54. Similarto the function of recuperator 44, pre-CAC 52 serves to raise thetemperature level of the liquid working fluid entering pre-CAC 52 whilecooling the air entering pre-CAC 52. Charge air exiting pre-CAC 52travels to a charge air cooler (not shown). The charge air coolerfurther reduces the temperature of charge air before that air enters thecylinders (not shown) of engine system 10.

Liquid working fluid exiting pre-CAC 52 travels downstream throughexhaust conduit 58 to exhaust heat exchanger 56. Exhaust heat exchanger56 receives some or all exhaust gas from an upstream aftertreatmentsystem 60, which is directed to exhaust heat exchanger 56 byaftertreatment conduit 64, proportional exhaust gas control valve 62 andfirst exhaust gas conduit 66. Exhaust gas control valve 62 directs hotexhaust gas through exhaust heat exchanger 56 based on the temperatureof exhaust heat exchanger 56. Temperature sensors may be located inexhaust gas heat exchanger 56, EGR boiler/superheater 74 or otherlocations to determine whether exhaust gas heat exchanger 56 is at anappropriate temperature to raise the temperature of the liquid workingfluid received from exhaust conduit 58 prior to exiting exhaust gas heatexchanger 56 by way of downstream EGR conduit 76. Exhaust gas travelingthrough exhaust heat exchanger 56 travels downstream by way of thirdexhaust gas conduit 70 to tailpipe or exhaust pipe 72. To preventexhaust gas heat exchanger 56 from overheating, exhaust gas controlvalve 62 can limit the heat load on exhaust gas heat exchanger 56 bydiverting some or all exhaust gas around exhaust heat exchanger 56downstream through second exhaust gas conduit 68 to tailpipe or exhaustpipe 72.

The temperature of the liquid working fluid has been raised three times,first by receiving heat from hot vaporized working fluid in recuperator44, second by receiving heat from the turbocharger compressor in pre-CAC52, which is downstream of recuperator 44, and third by receiving heatfrom exhaust gases in exhaust gas heat exchanger 56, which is downstreamof pre-CAC 52. The liquid working fluid now travels downstream to inlet74 d of EGR boiler/superheater 74 by way of EGR conduit 76. Exhaustgases exiting the exhaust manifold (not shown) of engine system 10 thatare part of an exhaust gas recirculating (EGR) system enter EGRboiler/superheater 74 at EGR inlet 74 a. Exhaust gas from the EGR systemflows through EGR boiler/superheater 74, which may take the place of anEGR cooler. The exhaust gas is cooled in EGR boiler/superheater 74 whiletransferring heat to the liquid working fluid, causing the liquidworking fluid, which has been pre-warmed as previously described, toboil and to produce a high-pressure vapor or gas that exits EGRboiler/superheater 74 at EGR outlet 74 e. The vaporized working fluidthen travels downstream via first conversion device conduit 80 to energyconversion device 78. For simplicity, EGR boiler/superheater 74 may becalled EGR boiler 74 or boiler 74 hereinafter. The exhaust gas exits EGRboiler/superheater 74 at EGR outlet 74 b to return to the EGR system.

High-pressure energy conversion device 78 may drive auxiliary device 82.Auxiliary device 82 can channel mechanical energy into the driveline(not shown) of engine system 10 or can generate electrical energy topower electrical devices or for storage in one or more batteries. Ifauxiliary device 82 is an electrical generator, the power could power adriveline motor generator (not shown) by way of power electronics (notshown) to help drive a vehicle (not shown) in which engine system 10 ismounted.

The vaporized or gaseous working fluid flows downstream through secondconversion device conduit 84 to recuperator 44. As previously noted, thegaseous working fluid entering recuperator 44 from second conversionconduit 84 is relatively hot compared to the liquid working fluidentering recuperator 44 from upstream recuperator conduit 46. Becauserecuperator 44 acts as a heat exchanger, heat is transferred from thegaseous working fluid to the liquid working fluid entering recuperator44 from upstream recuperator conduit 46. The gaseous working fluid nextflows downstream through condenser conduit 88 to condenser 18. Condenser18 has cooling air or fluid flowing through it to cool the gaseousworking fluid, returning the gaseous working fluid to a liquid state.The working fluid, now returned to a liquid state, flows downstreamthrough fluid passages that may be in base plate 24 to return tosub-cooler 16. Note that receiver 20 vents by way of receiver ventconduit 86 to condenser conduit 88, permitting the level of liquidworking fluid in receiver 20 to raise and lower as needed.

The system described thus far is a Rankine cycle waste heat recoverysystem or an organic Rankine cycle if the working fluid is an organichigh molecular mass fluid with a liquid-vapor phase change that is lowerthan the water-steam phase change. Examples of Rankine cycle workingfluids, organic and inorganic, include Genetron® R-245fa from Honeywell,Therminol®, Dowtherm J™ from Dow Chemical Co., Fluorinol® from AmericanNickeloid, toluene, dodecane, isododecane, methylundecane, neopentane,neopentane, octane, water/methanol mixtures, or steam. While the systemdescribed above may be a Rankine cycle or an organic Rankine cycle, italso presents an opportunity with respect to the exhaust gasrecirculation (EGR) system.

Current EGR systems are passive devices without the ability to regulateEGR cooler output temperature actively. The present disclosure describesa configuration that provides an ability to regulate EGR outlettemperature by using a partial bypass of recuperator 44 while stillmaintaining Rankine cycle efficiency and the improved fuel economyyielded by EGR. As previously noted, recuperator 44 provides a heatexchange between gaseous working fluid entering recuperator 44 fromupstream second conversion device conduit 84 and liquid working fluidentering recuperator 44 from upstream recuperator conduit 46. The liquidworking fluid then travels downstream to pre-CAC 52, then to exhaustheat exchanger 56 and then to EGR boiler/superheater 74, thus gainingthe benefits of interfacing with these components. However, a portion ofthe liquid working fluid bypasses recuperator 44 in a parallel path byway of first boiler control valve conduit 50, EGR boiler flow controlvalve 48, and second boiler control valve conduit 51. EGR boiler flowcontrol valve 48 may be a proportional valve that permits a portion ofthe liquid working fluid to bypass recuperator 44. Alternatively, EGRboiler flow control valve 48 may be modulated to open and close toadjust the amount of liquid working fluid entering second boiler controlvalve conduit 51.

The liquid working fluid that bypasses recuperator 44 connectsdownstream to inlet 74 c of EGR boiler/superheater 74 by way of secondboiler control valve conduit 51. The liquid working fluid that entersEGR boiler/superheater 74 by way of valve conduit 51 goes tolow-temperature section 25 of the EGR boiler/superheater 74, which isalso an EGR exhaust gas cooler, to regulate, control or adjust thetemperature of the exhaust gas that exits EGR boiler/superheater 74 atEGR outlet 74 b. This regulation is possible because the liquid workingfluid entering inlet 74 c is at a much lower temperature than the liquidworking fluid entering EGR boiler/superheater 74 from EGR conduit 76.The liquid working fluid entering EGR boiler/superheater 74 at EGR inlet74 c may be at a much lower temperature than the exhaust gas enteringEGR inlet 74 a. Thus, by adjusting the amount of liquid working fluidthat enters EGR boiler/superheater 74 by way of second boiler controlvalve conduit 51, engine system 10 and waste heat recovery circuit 14have the capability to regulate, control or adjust the temperature ofEGR exhaust gas that enters EGR inlet 74 a and exits EGR outlet 74 b.The capability of regulating the temperature of EGR exhaust gas isaccomplished by changing the flow rate of the coolest liquid workingfluid within EGR boiler/superheater 74. The benefit to the ability toadjust the temperature of the EGR exhaust gas is that increased coolingof EGR exhaust gas when the engine is hot increases the efficiency ofthe engine and generally leads to lower emissions of NOx from theengine. However, excessive cooling may lead to undesirable condensation,so temperature monitoring within EGR boiler/superheater 74 is importantto maintain the temperature of EGR exhaust gas within a functionallyuseful range. Decreasing cooling of EGR exhaust gas increases enginetemperature, which is beneficial when the engine is cold so that theengine reaches an optimal operating temperature more quickly. Decreasingcooling of EGR exhaust gas is also beneficial for thermal management ofthe aftertreatment system, which includes regeneration of certainelements of the aftertreatment system.

Control module 150 may regulate the function of boiler 74. Controlmodule 150 does this by receiving signals from various temperaturesensors and then controlling various valves located in engine system 10.For example, some situations may require additional heat to cause theliquid working fluid to boil, which control module 150 might determineby receiving a temperature and pressure signal from temperature andpressure sensor 23 located in higher temperature portion 27 of boiler74. The temperature and pressure signal from sensor 23 may indicate thatthe superheat of the vaporized working fluid is lower than a targetvalue. Control module 150 may also read the temperature of EGR exhaustgas entering boiler 74 by receiving a temperature signal from first EGRtemperature sensor 15 and using that signal to determine whetheradditional heat needs applied to the liquid working fluid to increasethe superheat of the vaporized working fluid. Control module 150 maythen command exhaust gas control valve 62 to increase the amount ofexhaust gas flow to exhaust heat exchanger 56 to increase thetemperature of the liquid working fluid flowing through conduit 76 toboiler 74. Control module 150 may also close EGR boiler flow controlvalve 48 to increase the flow of liquid working fluid throughrecuperator 44, pre-CAC 52 and exhaust heat exchanger 56 to increase theamount of heat transferred to the liquid working fluid. Control module150 may also reduce the flow rate of feed pump 32 or bypass liquidworking fluid through feed pump flow valve 34 back to receiver 20, whichresults in a decreased flow rate through recuperator 44, pre-CAC 52, andexhaust heat exchanger 56, which increases the temperature of thevaporized working fluid at the inlet of energy conversion device 78.Control module 150 may also increase the flow of EGR exhaust gas intoinlet 74 a of boiler 74 by modulating an EGR valve (not shown).

While vaporization or boiling of the liquid working fluid is animportant function of EGR boiler/superheater 74, EGR boiler/superheater74 also functions as an EGR cooler. The configuration of boiler 74allows boiler 74 to boil or vaporize the liquid working fluid whilecontinuing to provide cooling of the EGR exhaust gas. Second EGRtemperature sensor 17 may indicate inadequate cooling of EGR exhaust gasas it prepares to exit outlet 74 b of boiler 74. Control module 150 mayactuate EGR boiler flow control valve 48 upstream of inlet 74 c toincrease the amount of relatively cool liquid working fluid enteringinlet 74 c of boiler 74 into lower temperature portion 25 of boiler 74.The relatively low temperature of the liquid working fluid providesadditional cooling of EGR exhaust gas prior to the EGR exhaust gasreturning to the EGR system. Liquid working fluid flows through boilerportion 25 into higher temperature boiler portion 27, joining withliquid working fluid that enters boiler 74 from inlet 74 d at junction29. The higher temperature of the liquid working fluid entering inlet 74d in combination with the temperature of the EGR exhaust gas acts toquickly convert the liquid working fluid into a vapor, which proceedsthrough outlet 74 e to conduit 80 and then downstream to energyconversion device 78. Thus, the configuration of boiler 74 permits EGRboiler 74 to provide cooling to EGR exhaust gas while converting liquidworking fluid to a vapor. This same process may also adjust thesuperheat of the vaporized working fluid by decreasing the temperatureand pressure of the vaporized working fluid by taking one or more of theactions described hereinabove.

Referring now to FIG. 2, an engine system 110 in accordance with asecond exemplary embodiment of the present disclosure is shown. Enginesystem 110 includes a waste heat recovery circuit 114, fluid managementcircuit 12, and a portion of exhaust circuit 11. Elements in thisembodiment having the same number as the first embodiment work asdescribed in the first embodiment and are discussed again only asnecessary for clarity.

In this embodiment, second boiler control valve conduit 51 connects toan inlet 174 c of an EGR boiler 174. Recuperator 44 connects todownstream pre-CAC 52 by a pre-CAC conduit 90. Connected to andextending downstream from pre-CAC conduit 90 is a third boiler valveconduit 92. A second EGR boiler flow control valve 94 may connect tothird boiler valve conduit 92. A fourth boiler valve conduit 96 connectssecond EGR boiler flow control valve 94 to a downstream inlet 174 e ofEGR boiler 174. Pre-CAC 52 connects downstream to exhaust heat exchanger56 as described in the previous embodiment, and exhaust circuit 11 is asdescribed in the previous embodiment. Exhaust heat exchanger 56 connectsto a downstream inlet 174 d of EGR boiler 174 by way of EGR conduit 76.EGR boiler 174 also includes an EGR inlet 174 a and an EGR outlet 174 b.

Engine system 110 includes a control module or control system 250.Control module 250, which may be a single processor, a distributedprocessor, an electronic equivalent of a processor, or any combinationof the aforementioned elements, as well as software, electronic storage,fixed lookup tables and the like, is connected to certain components offluid management circuit 12 and waste heat recovery circuit 114 by awire harness 135, though such connection may be by other means, such asa wireless system.

Control module 250 connects to fluid level sensor 13 associated withsub-cooler 16. Control module 250 connects to feed pump flow valve 34,EGR boiler flow control valve 48, exhaust gas control valve 62, andsecond EGR boiler flow control valve 94. Control module 250 may connectto feed pump 32. Control module 250 may also connect to temperaturesensors positioned within EGR boiler/superheater 174 or in otherlocations. Referring to FIG. 5B, control module 250 may connect to afirst EGR temperature sensor 111, a second EGR temperature sensor 113, athird EGR temperature sensor 115, a fourth EGR temperature sensor 117, afirst working fluid temperature sensor 119, a second working fluidtemperature sensor 121, and a third working fluid temperature sensor 123and a temperature and pressure sensor 129. Temperature sensor 117 andtemperature sensor 119 may be located in a lower temperature portion 125of EGR boiler/superheater 174. Temperature sensor 115 and temperaturesensor 121 may be located in a moderate temperature portion 126 of EGRboiler/superheater 174. Temperature sensor 111, temperature sensor 113,temperature sensor 123, and temperature and pressure sensor 129 may belocated in a higher temperature portion 127 of EGR boiler/superheater174.

The second embodiment is similar in many respects to the firstembodiment, with one key difference. In addition to the liquid workingfluid that bypasses recuperator 44 and connects downstream to inlet 174c of EGR boiler/superheater 174 by way of second boiler control valveconduit 51, and the liquid working fluid that enters inlet 174 d, liquidworking fluid also enters a third inlet 174 e. The liquid working fluidin pre-CAC conduit 90 has a higher temperature than the temperature ofthe liquid working fluid in conduit 51, but the temperature of theliquid working fluid in pre-CAC conduit 90 is lower than the temperatureof the liquid working fluid in conduit 76.

The benefit to this configuration is that the temperature of the EGRexhaust gas may be adjusted, regulated or cooled with greater precisionby having the ability to select from three different liquid workingfluid temperatures. The lowest temperature is from second boiler controlvalve conduit 51, an intermediate temperature is from fourth boilervalve conduit 96, and a relatively high temperature is from EGR conduit76. Note that all three temperatures might be relatively low incomparison with the EGR exhaust gas entering inlet 174 a. As with thefirst embodiment, decreasing cooling of EGR exhaust gas increases enginetemperature, which is beneficial when the engine is cold so that theengine reaches an optimal operating temperature more quickly. Decreasingcooling of EGR exhaust gas is also beneficial for thermal management ofthe aftertreatment system, which includes regeneration of certainelements of the aftertreatment system.

Note also that while this embodiment contains second EGR boiler controlvalve 94, which may be a proportional valve that is adjustable, EGRboiler control valve 94 may be eliminated in some embodiments andreplaced with an aperture having a fixed diameter or by using a reduceddiameter conduit to restrict flow to inlet 174 e. While thisconfiguration has less flexibility than a configuration using anadjustable valve, a fixed amount of liquid working fluid at anintermediate temperature entering the EGR boiler may be beneficial inregulating the temperature limits of the EGR exhaust gas.

Control module 250 may regulate the function of boiler 174. Controlmodule 250 does this by receiving signals from various temperaturesensors and then controlling various valves located in engine system110. For example, some situations may require additional heat to causethe liquid working fluid to boil, which control module 250 mightdetermine by receiving a temperature signal from temperature andpressure sensor 129 located in higher temperature portion 127 of boiler174. The temperature and pressure signal from sensor 129 may indicatethat the superheat is lower than target. Control module 250 may read thetemperature of EGR exhaust gas entering boiler 174 by receiving atemperature signal from first EGR temperature sensor 111 and using thatsignal to determine whether additional heat needs applied to the liquidworking fluid. Control module 250 may then command exhaust gas controlvalve 62 to increase the amount of downstream exhaust gas flow toexhaust heat exchanger 56 to increase the temperature of the liquidworking fluid flowing through conduit 76 to boiler 174. Control module250 may also close EGR boiler flow control valve 48 to increase the flowof liquid working fluid through recuperator 44, pre-CAC 52 and exhaustheat exchanger 56 to increase the amount of heat transferred to theliquid working fluid. Control module 250 may also close EGR boiler flowcontrol valve 94 to increase the flow of liquid working fluid throughpre-CAC 52 and exhaust heat exchanger 56 to increase the amount of heattransferred to the liquid working fluid. Control module 250 may alsoreduce the flow rate of feed pump 32 or bypass liquid working fluidthrough feed pump flow valve 34 back to receiver 20, which results in adecreased flow rate through recuperator 44, pre-CAC 52, and exhaust heatexchanger 56, which increases heat transferred to the liquid workingfluid and increases the temperature of the vaporized working fluid atthe inlet of energy conversion device 78. Control module 250 may alsoincrease the flow of EGR exhaust gas into inlet 174 a of boiler 174 bymodulating an EGR valve (not shown).

While vaporization or boiling of the liquid working fluid is animportant function of EGR boiler/superheater 174, EGR boiler/superheater174 also functions as an EGR cooler. The configuration of boiler 174allows boiler 174 to boil or vaporize the liquid working fluid whilecontinuing to provide cooling of the EGR exhaust gas. Second EGRtemperature sensor 115 and third EGR temperature sensor 117 may indicateinadequate cooling of EGR exhaust gas as it travels through moderatetemperature section 126 and low temperature section 125 of boiler 174 asthe EGR exhaust gas travels through boiler 174 and then prepares to exitoutlet 174 b of boiler 174. Control module 250 may actuate EGR boilerflow control valve 48 to increase the amount of relatively cool liquidworking fluid entering inlet 174 c of boiler 174 into lower temperatureportion 125 of boiler 174. The relatively low temperature of the liquidworking fluid entering lower temperature portion 125, measured bytemperature sensor 119, provides additional cooling of EGR exhaust gasprior to the EGR exhaust gas returning to the EGR system. Liquid workingfluid flows through boiler portion 125 into moderate temperature portion126, joining with liquid working fluid that entered boiler 174 frominlet 174 e at junction 131. The temperature of the liquid working fluidentering inlet 174 e, measured by temperature sensor 121, provides somecooling of the EGR exhaust gas prior to the EGR exhaust gas traveling tolow temperature portion 125. The liquid working fluid continues to gainheat as it travels through moderate temperature portion 126. The liquidworking fluid then travels into higher temperature boiler portion 127,joining with liquid working fluid that enters boiler 174 from inlet 174d at junction 133. The higher temperature of the liquid working fluidentering inlet 174 d, measured by temperature sensor 123, in combinationwith the temperature of the EGR exhaust gas acts to quickly convert theliquid working fluid into a vapor, which proceeds through outlet 174 fto conduit 80 and then downstream to energy conversion device 78. Thevarious temperature sensors in combination with the various valves ofthe system regulate the amount of cooling provided to EGR exhaust gas asit travels through the various portions of boiler 174 while regulatingthe amount of heating provided to the liquid working fluid, thusimproving the amount of cooling provided to the EGR exhaust gas whileassuring the liquid working fluid vaporizes.

As with the previous embodiment, the superheat of the vaporized workingfluid needs to be within a targeted range in order to optimizeperformance of WHR system 110. Adjusting the opening of the valvesdescribed hereinabove and taking the actions described hereinaboveadjusts the temperature of the liquid working fluid, which also affectsthe superheat of the vaporized working fluid. Thus, if superheat needsreduced, heat transfer to the liquid working fluid is reduced, or for agiven heat input, the flow rate to the heat exchangers is increased byreducing the amount of feed pump bypass valve 34. If superheat needsincreased, heat transfer to the liquid working fluid is increased, orfor a given heat input, the flow rate to the heat exchangers is reducedby bypassing increased flow rate at the feed pump bypass valve 34.

Referring now to FIG. 3, an engine system 210 in accordance with a thirdexemplary embodiment of the present disclosure is shown. An enginesystem 210 includes a waste heat recovery circuit 214, fluid managementcircuit 12, and a portion of exhaust circuit 11. Elements in thisembodiment having the same number as the first embodiment work asdescribed in the first embodiment and are discussed again only asnecessary for clarity.

In this embodiment, second boiler control valve conduit 51 connects toan inlet 274 c of an EGR boiler/superheater 274. Recuperator 44 connectsdownstream to exhaust cooler 56 by an exhaust conduit 98. Connected toand extending downstream from exhaust conduit 98 is a third boiler valveconduit 100. A second EGR boiler flow control valve 102 may connect tothird boiler valve conduit 100. A fourth boiler valve conduit 104connects second EGR boiler flow control valve 102 to a downstream inlet274 e of EGR boiler 274. Heat exchanger 56 is as described in the firstexemplary embodiment, and exhaust circuit 11 is as described in thefirst exemplary embodiment. Exhaust heat exchanger 56 connects to aninlet 274 d of EGR boiler 274 by way of EGR conduit 76. EGR boiler 274also includes an EGR inlet 274 a and an EGR outlet 274 b.

Engine system 210 includes a control module or control system 350.Control module 350, which may be a single processor, a distributedprocessor, an electronic equivalent of a processor, or any combinationof the aforementioned elements, as well as software, electronic storage,fixed lookup tables and the like, is connected to certain components offluid management circuit 12 and waste heat recovery circuit 214 by awire harness 235, though such connection may be by other means, such asa wireless system.

Control module 350 connects to fluid level sensor 13 associated withsub-cooler 16. Control module 350 connects to feed pump flow valve 34,EGR boiler flow control valve 48 and EGR boiler flow control valve 102.Control module 350 may connect to feed pump 32. Control module 350 mayalso connect to temperature sensors positioned within EGRboiler/superheater 274 or in other locations. Referring to FIG. 5C,control module 350 may connect to a first EGR temperature sensor 211, asecond EGR temperature sensor 213, a third EGR temperature sensor 215, afourth EGR temperature sensor 217, a first working fluid temperaturesensor 219, a second working fluid temperature sensor 221, a thirdworking fluid temperature sensor 223 and a temperature and pressuresensor 229. Temperature sensor 217 and temperature sensor 219 may belocated in a lower temperature portion 225 of EGR boiler/superheater274. Temperature sensor 215 and temperature sensor 221 may be located ina moderate temperature portion 226 of EGR boiler/superheater 274.Temperature sensor 211, temperature sensor 213, temperature sensor 223,and temperature and pressure sensor 229 may be located in a highertemperature portion 227 of EGR boiler/superheater 274.

The third embodiment operates similarly in many respects to the secondembodiment, with one key difference. In this embodiment, there is nopre-charge air cooler. However, any heat transfer to the working fluidlost in the elimination of a pre-charge air cooler may be offset byincreasing heat transfer in exhaust heat exchanger 56 or in EGR boiler274, if increased heat transfer is necessary or desirable. As with thesecond embodiment, in addition to the liquid working fluid that bypassesrecuperator 44 and connects downstream to inlet 274 c of EGRboiler/superheater 274 by way of second boiler control valve conduit 51and the liquid working fluid that enters inlet 274 d, liquid workingfluid also enters a third inlet 274 e. The liquid working fluid infourth boiler valve conduit 104 has a higher temperature than thetemperature of the liquid working fluid in conduit 51, but thetemperature of the liquid working fluid in fourth boiler valve conduit104 is lower than the temperature of the liquid working fluid in conduit76. The benefit to this configuration is that the temperature of the EGRexhaust gas may be adjusted, regulated or cooled with greater precisionby having the ability to select from three different liquid workingfluid temperatures. The lowest temperature is from second boiler controlvalve conduit 51, an intermediate temperature is from fourth boilervalve conduit 104, and a relatively high temperature is from EGR conduit76. Note that all three temperatures might be relatively low incomparison with the temperature of EGR exhaust gas entering inlet 274 a.As with the first embodiment, decreasing cooling of EGR exhaust gasincreases engine temperature, which is beneficial when the engine iscold so that the engine reaches an optimal operating temperature morequickly. Decreasing cooling of EGR exhaust gas is also beneficial forthermal management of the aftertreatment system, which includesregeneration of certain elements of the aftertreatment system.

Control module 350 may regulate the function of boiler 274. Controlmodule 350 does this by receiving signals from various temperaturesensors and then controlling various valves located in engine system210. For example, some situations may require additional heat to causethe liquid working fluid to boil, which control module 350 mightdetermine by receiving a temperature signal from temperature andpressure sensor 229 located in higher temperature portion 227 of boiler274. The temperature and pressure signal from sensor 229 may indicatethat the superheat is lower than target. Control module may read thetemperature of EGR exhaust gas entering boiler 274 by receiving atemperature signal from first EGR temperature sensor 211 and using thatsignal to determine whether additional heat needs applied to the liquidworking fluid. Control module 350 may then command exhaust gas controlvalve 62 to increase the amount of downstream exhaust gas flow toexhaust heat exchanger 56 to increase the temperature of the liquidworking fluid flowing through conduit 76 to boiler 274. Control module350 may also close EGR boiler flow control valve 48 to increase the flowof liquid working fluid through recuperator 44 and exhaust heatexchanger 56 to increase the amount of heat transferred to the liquidworking fluid. Control module 350 may also close EGR boiler flow controlvalve 102 to increase the flow of liquid working fluid through exhaustheat exchanger 56 to increase the amount of heat transferred to theliquid working fluid. Control module 350 may also reduce the flow rateof feed pump 32 or bypass liquid working fluid through feed pump flowvalve 34 back to receiver 20, which results in a decreased flow ratethrough recuperator 44 and exhaust heat exchanger 56, which increasesheat transferred to the liquid working fluid. Control module 350 mayalso increase the flow of EGR exhaust gas into inlet 274 a of boiler 274by modulating an EGR valve (not shown).

While vaporization or boiling of the liquid working fluid is animportant function of EGR boiler/superheater 274, EGR boiler/superheater274 also functions as an EGR cooler. The configuration of boiler 274allows boiler 274 to boil or vaporize the liquid working fluid whilecontinuing to provide cooling of the EGR exhaust gas. Second EGRtemperature sensor 215 and third EGR temperature sensor 217 may indicateinadequate cooling of EGR exhaust gas as it travels through moderatetemperature section 226 and low temperature section 225 of boiler 274 asthe EGR exhaust gas travels through boiler 274 and then prepares to exitoutlet 274 b of boiler 274. Control module 350 may actuate EGR boilerflow control valve 48 to increase the amount of relatively cool liquidworking fluid entering inlet 274 c of boiler 274 into lower temperatureportion 225 of boiler 274. The relatively low temperature of the liquidworking fluid entering lower temperature portion 225, measured bytemperature sensor 219, provides additional cooling of EGR exhaust gasprior to the EGR exhaust gas returning to the EGR system. Liquid workingfluid flows through low temperature portion 225 into moderatetemperature portion 226, joining with liquid working fluid that entersboiler 274 from inlet 274 e at a junction 231. The temperature of theliquid working fluid entering inlet 274 e, measured by temperaturesensor 221, provides some cooling of the EGR exhaust gas prior to theEGR exhaust gas traveling to low temperature portion 225. The liquidworking fluid continues to gain heat as it travels downstream throughmoderate temperature portion 226. The liquid working fluid then travelsinto higher temperature boiler portion 227, joining with liquid workingfluid that enters boiler 274 from inlet 274 d at junction 233. Thehigher temperature of the liquid working fluid entering inlet 274 d,measured by temperature sensor 223, in combination with the temperatureof the EGR exhaust gas entering boiler 274 at inlet 274 a, acts toquickly convert the liquid working fluid into a vapor, which proceedsthrough outlet 274 f to conduit 80 and then downstream to energyconversion device 78. The various temperature sensors in combinationwith the various valves of the system regulate the amount of coolingprovided to EGR exhaust gas as it travels through the various portionsof boiler 274 while regulating the amount of heating provided to theliquid working fluid, thus improving the amount of cooling provided tothe EGR exhaust gas while assuring the liquid working fluid vaporizes.

As with the previous embodiment, the superheat of the vaporized workingfluid needs to be within a targeted range in order to optimizeperformance of WHR system 210. Adjusting the opening of the valvesdescribed hereinabove and taking the actions described hereinaboveadjusts the temperature of the liquid working fluid, which also affectsthe superheat of the vaporized working fluid. Thus, if superheat needsreduced, heat transfer to the liquid working fluid is reduced. Ifsuperheat needs increased, heat transfer to the liquid working fluid isincreased.

Referring now to FIG. 4, an engine system 310 in accordance with afourth exemplary embodiment of the present disclosure is shown. Enginesystem 310 includes a waste heat recovery circuit 314, fluid managementcircuit 12, and a portion of exhaust circuit 11. Elements in thisembodiment having the same number as previous embodiments work asdescribed in the first embodiment and are discussed again only asnecessary for clarity.

In this embodiment, second boiler control valve conduit 51 connects toan inlet 374 c of an EGR boiler 374. Recuperator 44 connects todownstream pre-CAC 52 by a pre-CAC conduit 90. Connected to andextending upstream from pre-CAC conduit 90 is a third boiler valveconduit 97. A second EGR boiler flow control valve 99 may connect tothird boiler valve conduit 97. A fourth boiler valve conduit 101connects second EGR boiler flow control valve 94 to an upstream outlet374 e of EGR boiler 374. Pre-CAC 52 connects downstream to exhaust heatexchanger 56 as described in the previous embodiment, and exhaustcircuit 11 is as described in the first two embodiments. Exhaust heatexchanger 56 connects to a downstream inlet 374 d of EGR boiler 374 byway of EGR conduit 76. EGR boiler 374 also includes an EGR inlet 374 aand an EGR outlet 374 b.

Engine system 310 includes a control module or control system 250.Control module 450, which may be a single processor, a distributedprocessor, an electronic equivalent of a processor, or any combinationof the aforementioned elements, as well as software, electronic storage,fixed lookup tables and the like, is connected to certain components offluid management circuit 12 and waste heat recovery circuit 314 by awire harness 335, though such connection may be by other means, such asa wireless system.

Control module 450 connects to fluid level sensor 13 associated withsub-cooler 16. Control module 450 connects to feed pump flow valve 34,EGR boiler flow control valve 48, exhaust gas control valve 62, andsecond EGR boiler flow control valve 99. Control module 450 may connectto feed pump 32. Control module 450 may also connect to temperaturesensors positioned within EGR boiler/superheater 374 or in otherlocations. Referring to FIG. 5B, control module 450 may connect to afirst EGR temperature sensor 111, a second EGR temperature sensor 113, athird EGR temperature sensor 115, a fourth EGR temperature sensor 117, afirst working fluid temperature sensor 141, a second working fluidtemperature sensor 143, a third working fluid temperature sensor 145, afourth working fluid temperature sensor 147, and a temperature andpressure sensor 149. Temperature sensor 117 and temperature sensor 141may be located in a lower temperature portion 153 of EGRboiler/superheater 374. Temperature sensor 115, temperature sensor 143,and temperature sensor 145 may be located in a moderate temperatureportion 154 of EGR boiler/superheater 374. Temperature sensor 111,temperature sensor 113, temperature sensor 147, and temperature andpressure sensor 149 may be located in a higher temperature portion 154of EGR boiler/superheater 374.

The fourth embodiment is similar in many respects to the secondembodiment, with one key difference. The liquid working fluid thatbypasses recuperator 44 and connects downstream to inlet 374 c of EGRboiler/superheater 374 by way of second boiler control valve conduit 51exits outlet 374 e of EGR boiler/superheater 374.

The benefit to this configuration is that the temperature of the EGRexhaust gas may be adjusted, regulated or cooled with greater precisionby having the ability to select from two different liquid working fluidtemperatures while subjecting the cooler liquid working fluid toadditional heat in Pre-CAC 52 and exhaust heat exchanger 56 prior to theliquid working fluid entering high temperature portion 154 of EGR boiler374. As with the first embodiment, decreasing cooling of EGR exhaust gasincreases engine temperature, which is beneficial when the engine iscold so that the engine reaches an optimal operating temperature morequickly. Decreasing cooling of EGR exhaust gas is also beneficial forthermal management of the aftertreatment system, which includesregeneration of certain elements of the aftertreatment system.

Note also that while this embodiment contains second EGR boiler controlvalve 99, which may be a proportional valve that is adjustable, EGRboiler control valve 99 may be eliminated in some embodiments.

Control module 450 may regulate the function of boiler 374. Controlmodule 450 does this by receiving signals from various temperaturesensors and then controlling various valves located in engine system310. For example, some situations may require additional heat to causethe liquid working fluid to boil, which control module 450 mightdetermine by receiving a temperature signal from temperature andpressure sensor 149 located in higher temperature portion 154 of boiler374. The temperature and pressure signal from sensor 149 may indicatethat the superheat is lower than target. Control module 450 may read thetemperature of EGR exhaust gas entering boiler 374 by receiving atemperature signal from first EGR temperature sensor 111 and using thatsignal to determine whether additional heat needs applied to the liquidworking fluid. Control module 450 may then command exhaust gas controlvalve 62 to increase the amount of downstream exhaust gas flow toexhaust heat exchanger 56 to increase the temperature of the liquidworking fluid flowing through conduit 76 to boiler 374. Control module450 may also close EGR boiler flow control valve 48 to increase the flowof liquid working fluid through recuperator 44, pre-CAC 52 and exhaustheat exchanger 56 to increase the amount of heat transferred to theliquid working fluid. Control module 450 may also adjust the flowthrough EGR boiler 374 by adjusting EGR boiler flow control valve 99.Control module 450 may also reduce the flow rate of feed pump 32 orbypass liquid working fluid through feed pump flow valve 34 back toreceiver 20, which results in a decreased flow rate through recuperator44, pre-CAC 52, and exhaust heat exchanger 56, which increases heattransferred to the liquid working fluid. Control module 450 may alsoincrease the flow of EGR exhaust gas into inlet 374 a of boiler 374 bymodulating an EGR valve (not shown).

While vaporization or boiling of the liquid working fluid is animportant function of EGR boiler/superheater 374, EGR boiler/superheater374 also functions as an EGR cooler. The configuration of boiler 374allows boiler 374 to boil or vaporize the liquid working fluid whileimproving cooling of the EGR exhaust gas. Second EGR temperature sensor115 and third EGR temperature sensor 117 may indicate inadequate coolingof EGR exhaust gas as it travels through moderate temperature section154 and low temperature section 153 of boiler 374 as the EGR exhaust gastravels through boiler 374 and then prepares to exit outlet 374 b ofboiler 374. Control module 450 may actuate EGR boiler flow control valve48 to increase the amount of relatively cool liquid working fluidentering inlet 174 c of boiler 174 into lower temperature portion 153 ofboiler 374. The relatively low temperature of the liquid working fluidentering lower temperature portion 153, measured by temperature sensor141, provides additional cooling of EGR exhaust gas prior to the EGRexhaust gas returning to the EGR system. Liquid working fluid flowsthrough boiler portion 153 into moderate temperature portion 154,exiting EGR boiler 374 at outlet 374 e. The temperature of the liquidworking fluid flowing through low temperature portion 153 and moderatetemperature portion 154 may be monitored with temperature sensor 143 andtemperature sensor 145, which assists control module 450 in determiningthe additional cooling capability of the liquid working fluid as well asthe additional heat that needs transferred to the liquid working fluidto boil. After passing through pre-CAC 52 and exhaust heat exchanger 56,the liquid working fluid enters EGR boiler 374 at inlet 374 d. Thehigher temperature of the liquid working fluid entering inlet 374 d,measured by temperature sensor 147, in combination with the temperatureof the EGR exhaust gas acts to quickly convert the liquid working fluidinto a vapor, which proceeds through outlet 374 f to conduit 80 and thendownstream to energy conversion device 78. The various temperaturesensors in combination with the various valves of the system regulatethe amount of cooling provided to EGR exhaust gas as it travels throughthe various portions of boiler 374 while regulating the amount ofheating provided to the liquid working fluid, thus improving the amountof cooling provided to the EGR exhaust gas while assuring the liquidworking fluid vaporizes.

As with the previous embodiment, the superheat of the vaporized workingfluid needs to be within a targeted range in order to optimizeperformance of WHR system 310. Adjusting the opening of the valvesdescribed hereinabove and taking the actions described hereinaboveadjusts the temperature of the liquid working fluid, which also affectsthe superheat of the vaporized working fluid. Thus, if superheat needsreduced, heat transfer to the liquid working fluid is reduced. Ifsuperheat needs increased, heat transfer to the liquid working fluid isincreased.

While various embodiments of the disclosure have been shown anddescribed, it is understood that these embodiments are not limitedthereto. The embodiments may be changed, modified and further applied bythose skilled in the art. Therefore, these embodiments are not limitedto the detail shown and described previously, but also include all suchchanges and modifications.

We claim:
 1. A waste heat recovery system for an internal combustionengine, the waste heat recovery system comprising: a fluid managementcircuit, including: a sub-cooler containing a liquid working fluid; apump fluidly connected to the sub-cooler and operable to draw the liquidworking fluid from the sub-cooler; a waste heat recovery circuit,including: a recuperator fluidly connected to the pump and configured toreceive a first portion of the liquid working fluid from the pump andreceive a vaporized working fluid, wherein heat is transferred from thevaporized working fluid to the first portion of the liquid workingfluid, and wherein the first portion of the liquid working fluid flowingfrom a liquid working fluid recuperator outlet is at a firsttemperature; a first EGR boiler flow control valve fluidly connected tothe pump in parallel with the recuperator so as to receive a secondportion of the liquid working fluid from the pump at a secondtemperature lower than the first temperature; and a boiler including afirst inlet fluidly connected to an exhaust circuit so as to receive EGRexhaust gas, a second inlet fluidly connected to the first EGR boilerflow control valve, and a third inlet fluidly connected to the liquidworking fluid recuperator outlet via a second EGR boiler flow controlvalve, wherein the boiler receives the first portion of the liquidworking fluid at the first temperature from the first EGR boiler flowcontrol valve; and at least a portion of the second portion of theliquid working fluid flowing from the recuperator at the secondtemperature; wherein heat is transferred from the EGR exhaust gas to theliquid working fluid to cause the liquid working fluid to vaporize; andwherein the liquid working fluid at the second temperature is used tocontrol the amount of cooling provided to the EGR exhaust gas.
 2. Thewaste heat recovery system of claim 1, further including a pre-chargeair cooler fluidly connected to the recuperator and receiving the liquidworking fluid from the recuperator and receiving charge air from aturbocharger compressor, wherein the pre-charge air cooler acts totransfer heat from the charge air to the liquid working fluid.
 3. Thewaste heat recovery system of claim 1, further including an energyconversion device fluidly connected to the boiler and receivingvaporized working fluid from the boiler.
 4. The waste heat recoverysystem of claim 3, wherein the energy conversion device is fluidlyconnected to the recuperator and the vaporized working fluid flows fromthe energy conversion device to the recuperator.
 5. The waste heatrecovery system of claim 1, wherein the recuperator is fluidly connectedto a condenser and the vaporized working fluid flows from therecuperator to the condenser.
 6. The waste heat recovery system of claim5, wherein the condenser is fluidly connected to the sub-cooler and thecondenser operates to convert the vaporized working fluid to the liquidworking fluid, and the liquid working fluid flows to the sub-cooler. 7.A waste heat recovery system for an internal combustion engine, thewaste heat recovery system comprising: a sub-cooler containing a liquidworking fluid; a pump fluidly connected to the sub-cooler and operableto draw the liquid working fluid from the sub-cooler; a recuperatorfluidly connected to the pump and configured to receive a first portionof the liquid working fluid from the pump and receive a vaporizedworking fluid from an EGR boiler, wherein heat is transferred from thevaporized working fluid to the first portion of the liquid working fluidand wherein the first portion of the liquid working fluid flowing from aliquid working fluid recuperator outlet is at a first temperature; aheat exchanger fluidly connected to the liquid working fluid recuperatoroutlet; a first EGR boiler flow control valve fluidly connected to thepump in parallel to the recuperator; a second EGR boiler flow controlvalve fluidly connected to the recuperator and connected to the EGRboiler, the second EGR boiler flow control valve fluidly connected tothe recuperator in parallel with the heat exchanger; wherein the EGRboiler includes a first inlet fluidly connected to an exhaust circuit soas to receive EGR exhaust gas, a second inlet fluidly connected to thefirst EGR boiler flow control valve, and a third inlet fluidly connectedto the liquid working fluid recuperator outlet via the second EGR boilerflow control valve, wherein the boiler receives the first portion of theliquid working fluid at the first temperature and at least a portion ofthe second portion of the liquid working fluid at a second temperaturelower than the first temperature; wherein heat is transferred from theEGR exhaust gas to the liquid working fluid to cause the liquid workingfluid to vaporize; and wherein the liquid working fluid at the firsttemperature and the liquid working fluid at the second temperature areused to control the amount of cooling provided to the EGR exhaust gas.8. The waste heat recovery system of claim 7, further including apre-charge air cooler fluidly connected to the recuperator and receivingthe liquid working fluid and receiving charge air from a turbochargercompressor, wherein the pre-charge air cooler acts to transfer heat fromthe charge air to the liquid working fluid.
 9. The waste heat recoverysystem of claim 8, further including an exhaust cooler fluidly connectedto the pre-charge air cooler and receiving the liquid working fluid fromthe pre-charge air cooler and receiving exhaust gas from anaftertreatment system, wherein the liquid working fluid from the exhaustcooler is fluidly connected to a fourth inlet of the boiler.
 10. Thewaste heat recovery system of claim 7, further including an exhaustcooler fluidly connected to the recuperator and receiving the liquidworking fluid from the recuperator and receiving exhaust gas from anaftertreatment system, wherein the exhaust cooler is fluidly connectedto a fourth inlet of the boiler.
 11. The waste heat recovery system ofclaim 7, further including an energy con version device fluidlyconnected to the boiler and receiving vaporized working fluid from theboiler.
 12. The waste heat recovery system of claim 11, wherein theenergy conversion device is fluidly connected to the recuperator and thevaporized working fluid flows from the energy conversion device to therecuperator.
 13. The waste heat recovery system of claim 7, wherein therecuperator is fluidly connected to a condenser and the vaporizedworking fluid flows from the recuperator to the condenser.
 14. The wasteheat recovery system of claim 13, wherein the condenser is fluidlyconnected to the sub-cooler and the condenser operates to convert thevaporized working fluid, to the liquid working fluid, and the liquidworking fluid flows to the sub-cooler.
 15. A method for using an EGRboiler control valve of a Rankine cycle to regulate EGR exhaust gastemperature in an engine, the method comprising: pumping a liquidworking fluid at a first temperature from a sub-cooler to the EGR boilercontrol valve; adjusting the EGR boiler control valve and selectivelydirecting a first portion of the liquid working fluid through at leastone heat exchanger, heating the first portion to a second temperature,and then directing the heated first portion to a first inlet of an EGRboiler and selectively directing a second portion of the liquid workingfluid through a bypass around the at least one heat exchanger to asecond inlet of the EGR boiler; passing EGR exhaust gas through the EGRboiler; wherein the second portion of the liquid working fluid at thefirst temperature is used to control an amount of cooling provided tothe EGR exhaust gas; and wherein the at least one heat exchangerincludes a recuperator and an exhaust heat exchanger.
 16. The method ofclaim 15, wherein the exhaust heat exchanger is fluidly connected to athird inlet of the EGR boiler.
 17. The method of claim 15, wherein theat least one heat exchanger includes a pre-charge air cooler, which isfluidly connected to the recuperator and wherein the precharge aircooler is fluidly connected to an the exhaust heat exchanger, andwherein the second portion of the liquid working fluid flows from therecuperator.